CN103076548B

CN103076548B - Method for predicting flashover voltage by using surface conductivity and leakage current

Info

Publication number: CN103076548B
Application number: CN201310040885.3A
Authority: CN
Inventors: 周志成; 赵晨龙; 高嵩; 张军广; 王黎明; 刘洋; 陶风波; 马勇; 路永玲; 陈杰
Original assignee: State Grid Corp of China SGCC; State Grid Jiangsu Electric Power Co Ltd; Shenzhen Graduate School Tsinghua University; Electric Power Research Institute of State Grid Jiangsu Electric Power Co Ltd
Current assignee: State Grid Corp of China SGCC; State Grid Jiangsu Electric Power Co Ltd; Shenzhen Graduate School Tsinghua University; Electric Power Research Institute of State Grid Jiangsu Electric Power Co Ltd
Priority date: 2013-02-01
Filing date: 2013-02-01
Publication date: 2015-04-29
Anticipated expiration: 2033-02-01
Also published as: CN103076548A

Abstract

The invention discloses a method for predicting flashover voltage by using surface conductivity and leakage current. The surface conductivity of an insulator is measured, and the surface conductivity of the insulator is used as an input parameter, combined with the shape coefficient parameter of the insulator to establish a dynamic arc model and calculate the leakage current development. According to the trend, the minimum flashover voltage of the insulator string is obtained, and the insulation margin and external insulation level of the insulator are judged based on the minimum flashover voltage. According to the measured overall conductivity of the insulator string, the present invention uses a dynamic arc model to calculate the development trend of the leakage current. The arc dynamic model describes the leakage current and the change rule of the arc length with time through mathematical equations, which is more in line with the real situation, and then realizes the insulation state judgment and pollution flashover warning purposes.

Description

A Method for Predicting Flashover Voltage Using Surface Conductivity and Leakage Current

技术领域technical field

本发明属于输电线路外绝缘状态评估领域，以绝缘子表面污层电导率作为输入参数，可仿真得到泄漏电流发展趋势，并预测绝缘子的闪络电压，进而评估输电线路的外绝缘水平，适用于输电线路广泛使用的瓷绝缘子和玻璃绝缘子。The invention belongs to the field of evaluation of the external insulation state of the transmission line. The conductivity of the dirty layer on the surface of the insulator is used as an input parameter to simulate the development trend of the leakage current, predict the flashover voltage of the insulator, and then evaluate the external insulation level of the transmission line. It is suitable for power transmission Porcelain insulators and glass insulators are widely used in lines.

背景技术Background technique

污闪是可能导致电力系统出现灾难性事故的重要原因之一。为保证电网的安全运行需要在污闪事故发生前能做出预警。闪络电压是表征绝缘子外绝缘性能的重要参数，通过测量、估算绝缘子串的闪络电压是评价绝缘子串外绝缘性能的有效方式。Pollution flashover is one of the important reasons that may lead to catastrophic accidents in power systems. In order to ensure the safe operation of the power grid, it is necessary to give an early warning before the pollution flashover accident occurs. Flashover voltage is an important parameter to characterize the external insulation performance of insulators. Measuring and estimating the flashover voltage of insulator strings is an effective way to evaluate the external insulation performance of insulator strings.

实测绝缘子串的污闪电压存在一定的难度。更重要的是在线预警技术需要在闪络发生前即可通过测量绝缘子的电气参数预估其闪络电压。It is difficult to measure the pollution flashover voltage of insulator strings. More importantly, the online early warning technology needs to estimate the flashover voltage by measuring the electrical parameters of the insulator before the flashover occurs.

静态模型对临界污闪状态的分析有很大的作用。但是，对于描述绝缘子电压、电流、电弧的动态变化过程存在明显的不足。The static model plays a very important role in the analysis of the critical pollution flashover state. However, there are obvious deficiencies in describing the dynamic change process of insulator voltage, current and arc.

发明内容Contents of the invention

本发明提供了一种用电导率和泄漏电流发展趋势预测闪络电压的方法，采用电弧动态模型通过数学方程来描述绝缘子泄漏电流以及电弧长度随时间的变化规律，更符合真实情况。The invention provides a method for predicting the flashover voltage by using the electric conductivity and the development trend of the leakage current. The arc dynamic model is used to describe the insulator leakage current and the change law of the arc length with time through mathematical equations, which is more in line with the real situation.

以绝缘子表面污层电导率作为输入参数，计算得到泄漏电流发展趋势，预测绝缘子的闪络电压，进而评估输电线路的外绝缘水平。Taking the conductivity of the polluted layer on the surface of the insulator as the input parameter, the development trend of the leakage current is calculated, the flashover voltage of the insulator is predicted, and the external insulation level of the transmission line is evaluated.

一种用表面电导率和泄漏电流预测闪络电压的方法，其特征在于，包括以下步骤：A method for predicting flashover voltage with surface conductivity and leakage current, is characterized in that, comprises the following steps:

（1）测量绝缘子表面电导率，(1) Measure the surface conductivity of the insulator,

（2）以绝缘子表面电导率作为输入参数，结合绝缘子形状系数参数，建立动态电弧模型，(2) Using the surface conductivity of the insulator as an input parameter, combined with the shape coefficient parameters of the insulator, a dynamic arc model is established,

（3）计算泄漏电流发展趋势，(3) Calculate the leakage current development trend,

（4）得到绝缘子串的最低闪络电压，基于最低闪络电压判断该绝缘子的绝缘裕度及外绝缘水平。(4) Obtain the minimum flashover voltage of the insulator string, and judge the insulation margin and external insulation level of the insulator based on the minimum flashover voltage.

建立动态电弧模型的步骤如下：The steps to establish a dynamic arc model are as follows:

设定绝缘子形状系数，给定参数的初始值；Set the shape factor of the insulator and give the initial value of the parameter;

输入测得的绝缘子表面电导率σ；Input the measured insulator surface conductivity σ;

假设在零时刻，电压u(t)达到波峰，燃弧开始：Assume that at time zero, the voltage u(t) reaches its peak and arcing begins:

u(t)=U_m cosωt （1）u(t)=U _m cosωt (1)

其中，U_m为电压有效值，ω为角频率，t为时间；Among them, U _m is the effective value of the voltage, ω is the angular frequency, and t is the time;

平板型悬式绝缘子剩余污层电阻随着弧根半径和电弧长度的变化公式：The formula for the variation of residual dirt layer resistance of flat suspension insulators with arc root radius and arc length:

${R R}_{p p} (({L L}_{arc arc})) = = \frac{11}{{πσ πσ}_{e e}} ln ln \frac{L L - - {L L}_{arc arc}}{{r r}_{00}} - - - - - - ((22))$

其中，L为泄漏距离总长度，L_arc为当前条件下的电弧长度；σ_e为表面污层电导率；r₀为弧根半径，由以下公式求得：Among them, L is the total length of the leakage distance, La _arc is the arc length under the current conditions; σ _e is the conductivity of the surface fouling layer; r ₀ is the radius of the arc root, which is obtained by the following formula:

${r r}_{00} = = \sqrt{\frac{{I I}_{arc arc}}{1.45 1.45 π π}} - - - - - - ((33))$

其中，该状态下对应的泄漏电流I_arc由公式（4）求得：Among them, the corresponding leakage current I _arc in this state is obtained by the formula (4):

${I I}_{arc arc} = = \frac{u u ((t t))}{{R R}_{p p} + + {r r}_{arc arc} {L L}_{arc arc}} - - - - - - ((44))$

其中，u(t)为此时电压，R_p为绝缘子剩余污层电阻，r_arc为单位长度的电弧电阻，L_arc为当前条件下的电弧长度；Among them, u(t) is the voltage at this time, R _p is the resistance of the remaining dirty layer of the insulator, r _arc is the arc resistance per unit length, and L _arc is the arc length under the current conditions;

由以下公式计算电弧场强E_arc和剩余污层场强E_p：The electric arc field strength E _arc and the residual pollution layer field strength E _p are calculated by the following formula:

E_arc＝63I_arc ^-0.5 （5）E _arc = 63 I _arc ^-0.5 (5)

${E E.}_{p p} = = 6363^{22 / / 33} {r r}_{p p}^{11 / / 33} - - - - - - ((66))$

电弧延伸条件为：The arc extension condition is:

E_arc<E_p （7）E _arc < E _p (7)

当E_p<E_arc时，随着电压的变化，电弧长度变化的表达式如式（8）所示：When E _p < E _arc , the expression of the arc length change with the voltage change is shown in formula (8):

$\frac{d d {L L}_{arc arc}}{dt dt} = = - - {L L}_{arc arc} ω ω sin sin ωt ωt - - - - - - ((88))$

当E_p＞E_arc时，电弧长度变化的表达式如式（9）所示：When E _p >E _arc , the expression of arc length change is shown in formula (9):

$\frac{d d {L L}_{arc arc}}{dt dt} = = - - {L L}_{arc arc} ω ω sin sin ωt ωt + + μ μ {E E.}_{arc arc} - - - - - - ((99))$

电弧长度变化还有附加的延伸参数μ；There is an additional extension parameter μ for arc length variation;

建立单位长度电弧电阻变化的动态方程：Establish the dynamic equation for the change of arc resistance per unit length:

$\frac{{dr dr}_{arc arc} ((t t))}{dt dt} = = \frac{{r r}_{arc arc} ((t t))}{τ τ} ((11 - - \frac{{I I}_{arc arc} {((t t))}^{22} {r r}_{arc arc} ((t t))}{{N N}_{00}})) - - - - - - ((1010))$

其中，N₀为单位长电弧的耗散功率；τ为时间常数，由下式计算：Among them, N ₀ is the dissipated power of the unit long arc; τ is the time constant, calculated by the following formula:

$τ τ = = \frac{{Q Q}_{00}}{{N N}_{00}} - - - - - - ((1111))$

其中，Q₀为试验所得耗散功率常数；Among them, _Q0 is the power dissipation constant obtained from the test;

定义电弧的熄灭条件为：The extinguishing condition of the arc is defined as:

R_arc＞R_n （12）R _arc > R _n (12)

其中R_arc为电弧总电阻，R_arc=r_arcL_arc；R_n为一个设定的电阻值，若此时由于电弧电阻远大于干区的电阻，电流通过干区后再流过剩余污层，电弧熄灭；Among them, R _arc is the total resistance of the arc, R _arc = r _arc L _arc ; R _n is a set resistance value, if the arc resistance is much greater than the resistance of the dry area at this time, the current will flow through the remaining dirty layer after passing through the dry area , the arc is extinguished;

电弧熄灭后，说明在此时的表面电导率σ下，U_m不足以使得绝缘子发生闪络，故增大U_m，直至得到一个最小的U_m，使得绝缘子发生闪络，此值即为得到的该绝缘子串的最低闪络电压。After the arc is extinguished, it means that under the surface conductivity σ at this time, U _m is not enough to make the insulator flashover, so increase U _m until a minimum U _m is obtained, which makes the insulator flashover, and this value is obtained The minimum flashover voltage of the insulator string.

上述公式中参数取值为：N₀=60，Q₀=0.075，μ=5。The values of the parameters in the above formula are: N ₀ =60, Q ₀ =0.075, μ=5.

本发明所达到的有益效果：The beneficial effect that the present invention reaches:

本发明的用电导率和泄漏电流发展趋势预测闪络电压的方法，以绝缘子表面电导率作为输入参数，通过输入测量所得绝缘子表面电导率，结合系统内置绝缘子形状系数参数，通过动态电弧模型计算泄漏电流发展趋势，进而最终得到绝缘子串的闪络电压，进而预测评估输电线路的外绝缘水平，实现绝缘状态判断与污闪预警的目的。本发明的方法采用电弧动态模型通过数学方程来描述绝缘子泄漏电流以及电弧长度随时间的变化规律，更符合真实情况，适用于输电线路广泛使用的瓷绝缘子和玻璃绝缘子。The method for predicting the flashover voltage using the conductivity and leakage current development trend of the present invention uses the surface conductivity of the insulator as an input parameter, and calculates the leakage through the dynamic arc model by inputting and measuring the surface conductivity of the insulator, combined with the built-in insulator shape factor parameters of the system Current development trend, and finally obtain the flashover voltage of the insulator string, and then predict and evaluate the external insulation level of the transmission line, so as to realize the purpose of insulation state judgment and pollution flashover warning. The method of the invention uses the arc dynamic model to describe the insulator leakage current and the time-varying law of the arc length through mathematical equations, which is more in line with the real situation, and is suitable for porcelain insulators and glass insulators widely used in power transmission lines.

附图说明Description of drawings

图1为计算流程图；Figure 1 is a calculation flow chart;

图2（a）为未发生闪络时的动态电弧模型仿真泄漏电流波形；泄漏电流波形对比图；Figure 2(a) is the simulation leakage current waveform of the dynamic arc model when no flashover occurs; the comparison diagram of the leakage current waveform;

图2（b）为未发生闪络时的实测泄漏电流波形；Figure 2(b) is the measured leakage current waveform when no flashover occurs;

图3（a）为发生闪络时的动态电弧模型仿真泄漏电流波形；泄漏电流波形对比图；Figure 3(a) is the leakage current waveform simulated by the dynamic arc model when flashover occurs; the comparison diagram of the leakage current waveform;

图3（b）为发生闪络时的实测泄漏电流波形Figure 3(b) is the measured leakage current waveform when flashover occurs

图4为污层整体电导率和污闪电压关系图。Figure 4 is a graph showing the relationship between the overall conductivity of the polluted layer and the pollution flashover voltage.

具体实施方式Detailed ways

下面结合附图对本发明作进一步描述。以下实施例仅用于更加清楚地说明本发明的技术方案，而不能以此来限制本发明的保护范围。The present invention will be further described below in conjunction with the accompanying drawings. The following examples are only used to illustrate the technical solution of the present invention more clearly, but not to limit the protection scope of the present invention.

如图1所示，计算开始时，设定绝缘子形状系数。As shown in Figure 1, at the beginning of the calculation, the shape factor of the insulator is set.

输入试验测得的绝缘子表面电导率σ，给定各个参数的初始值。Input the surface conductivity σ of the insulator measured by the test, and give the initial value of each parameter.

u(t)=U_m cosωt （1）u(t)=U _m cosωt (1)

其中，U_m为电压有效值，ω为角频率，t为时间。Among them, U _m is the effective value of the voltage, ω is the angular frequency, and t is the time.

平板型悬式绝缘子剩余污层电阻R_p随着弧根半径r₀和电弧长度L_arc的变化公式：The formula for the variation of the resistance R _p of the residual pollution layer of the flat suspension insulator with the radius r ₀ of the arc root and the length L _{arc of the arc} is:

其中，r₀为弧根半径；L为泄漏距离总长度，L_arc为当前条件下的电弧长度；σ_e为表面污层电导率；Among them, r ₀ is the radius of the arc root; L is the total length of the leakage distance, La _arc is the arc length under the current conditions; σ _e is the conductivity of the surface contamination layer;

r₀为弧根半径，由以下公式求得：r ₀ is the arc root radius, obtained by the following formula:

该状态下对应的泄漏电流I_arc（电弧电流）由公式（4）求得，表达式如下：The corresponding leakage current I _arc (arc current) in this state is obtained by the formula (4), and the expression is as follows:

E_arc和E_p分别为电弧场强和剩余污层场强。由以下公式计算：E _arc and E _p are the electric arc field strength and the remaining fouling layer field strength respectively. Calculated by the following formula:

E_arc=63I_arc ^-0.5 （5）E _arc =63I _arc ^-0.5 (5)

${E E.}_{p p} = = 6363^{22 / / 33} {r r}_{p p}^{11 / / 33} - - - - - - ((66))$

电弧延伸条件为：The arc extension condition is:

E_arc<E_p （7）E _arc < E _p (7)

当E_p<E_arc时，随着电压的变化，电弧长度变化的表达式如下：When E _p < E _arc , the expression of the change of arc length as the voltage changes is as follows:

当E_p＞E_arc时，电弧长度变化还有附加的延伸参数μ：When E _p > E _arc , the arc length change has an additional extension parameter μ:

单位长度电弧电阻变化的动态方程，如下式所示：The dynamic equation for the change of arc resistance per unit length is shown in the following formula:

其中，N₀为单位长电弧的耗散功率，τ为时间常数，由下式计算：Among them, N ₀ is the dissipated power of the unit long arc, τ is the time constant, calculated by the following formula:

$τ τ = = \frac{{Q Q}_{00}}{{N N}_{00}} - - - - - - ((1111))$

如果电弧的输入能量始终小于散失能量，电弧电阻将逐步增加，最终电弧逐渐熄灭。因此，定义电弧的熄灭条件为：If the input energy of the arc is always less than the dissipated energy, the arc resistance will gradually increase, and finally the arc will gradually extinguish. Therefore, the extinguishing condition of the defined arc is:

R_arc＞R_n （12）R _arc > R _n (12)

其中R_arc为电弧总电阻，R_arc=r_arcL_arc；R_n代表描述电弧熄灭的电阻，远大于常态下的电弧电阻，仿真中可取1MΩ（R_n取值只要足够大，就不会影响电弧发展时的电流和弧长变化趋势。同时该值可根据仿真结果加以优化，以提高计算效率）。当R_arc＞R_n时，由于电弧电阻远大于干区的电阻，因此电流通过干区后再流过剩余污层，电弧熄灭。Among them, R _arc is the total arc resistance, R _arc =r _arc L _arc ; R _n represents the resistance describing arc extinguishing, which is much larger than the arc resistance under normal conditions, and it can be 1MΩ in the simulation (as long as the value of R _n is large enough, it will not affect The trend of current and arc length when the arc develops. At the same time, this value can be optimized according to the simulation results to improve the calculation efficiency). When R _arc >R _n , since the arc resistance is much greater than the resistance of the dry area, the current flows through the dry area and then through the remaining dirt layer, and the arc is extinguished.

电弧熄灭后，说明在此时的表面电导率σ下，U_m不足以使得绝缘子发生闪络，故增大U_m，直至得到一个最小的U_m，使得绝缘子发生闪络。此值即为该串绝缘子的闪络电压。After the arc is extinguished, it means that under the surface conductivity σ at this time, U _m is not enough to make the insulator flashover, so U _m is increased until a minimum U _m is obtained, which makes the insulator flashover. This value is the flashover voltage of the string of insulators.

仿真时的电弧参数和实测参数有很大的不同，其中，影响仿真结果的最重要的是污层的耗散功率N₀，该参数决定了电弧能量的增减，直接影响电弧电阻的动态变化，进而影响绝缘子的污闪电压和泄漏电流变化规律。因此，本模型中使用的参数较佳地取值为：The arc parameters in the simulation are very different from the measured parameters. Among them, the most important factor affecting the simulation results is the power dissipation N ₀ of the fouling layer. This parameter determines the increase or decrease of the arc energy and directly affects the dynamic change of the arc resistance. , and then affect the pollution flashover voltage and leakage current of the insulator. Therefore, the preferred values of the parameters used in this model are:

N₀=60，Q₀=0.075，μ=5。N ₀ =60, Q ₀ =0.075, μ=5.

上述参数都是比例系数，单位取1。结果表明模型仿真结果和人工污秽试验结果符合度较好。The above parameters are proportional coefficients, and the unit is 1. The results show that the model simulation results are in good agreement with the artificial pollution test results.

对上述建立的动态电弧模型进行仿真，图2（a）、图2（b）和图3（a）、图3（b）分别为未发生污闪和发生污闪时候的泄漏电流仿真波形和实测波形的对比。仿真和实测的对象均为XP-70型绝缘子。由于电弧没有明显的熄灭、重燃现象，无论绝缘子是否发生污闪，模拟电流和实测电流波形非常相似。The dynamic arc model established above is simulated, and Fig. 2(a), Fig. 2(b) and Fig. 3(a), Fig. 3(b) respectively show the leakage current simulation waveforms and Comparison of measured waveforms. Both simulation and measurement objects are XP-70 insulators. Since there is no obvious phenomenon of extinguishing and re-ignition of the arc, the waveform of the simulated current and the measured current are very similar no matter whether the insulator has pollution flashover or not.

在未发生污闪时，泄漏电流先达到最大值，然后在几个周波内迅速减小。发生污闪时，在临闪前，泄漏电流均达到了安培级，泄漏电流逐步增大，最终电弧贯穿绝缘子而形成闪络。仿真波形和实测波形一个显著的差别是：在实测波形中，尽管电弧过零不熄灭，电流波形也有可能出现“零休”现象。例如实测未闪络波形电弧熄灭前的最后一个周波以及闪络波形的前一个周波。When no pollution flashover occurs, the leakage current first reaches the maximum value, and then decreases rapidly within a few cycles. When pollution flashover occurs, the leakage current reaches the ampere level before the flashover, and the leakage current gradually increases, and finally the arc penetrates the insulator to form a flashover. A significant difference between the simulated waveform and the measured waveform is that in the measured waveform, although the arc does not go out when it crosses zero, the current waveform may also have a "zero break" phenomenon. For example, the last cycle before the arc extinguishment of the non-flashover waveform and the previous cycle of the flashover waveform are measured.

为了进一步验证模型的准确性，对X-4.5型悬式绝缘子在相同污层整体电导率下的污闪电压的理论计算结果和试验结果进行了比较，比较结果如图4所示。可以发现，试验结果和仿真结果的差异很小，证明了该染污放电模型对污闪电压的预测符合实际情况。In order to further verify the accuracy of the model, the theoretical calculation results and experimental results of the pollution flashover voltage of the X-4.5 type suspension insulator under the same overall conductivity of the polluted layer were compared. The comparison results are shown in Figure 4. It can be found that the difference between the test results and the simulation results is very small, which proves that the pollution discharge model's prediction of the pollution flashover voltage is in line with the actual situation.

本方法在剩余污层电阻、电弧发展速度、电弧熄灭条件、仿真参数等方面建立了与实测波形相似、试验结果吻合的染污放电泄漏电流仿真模型。试验结果和模型仿真结果得到了相互验证。This method establishes a pollution discharge leakage current simulation model that is similar to the measured waveform and coincides with the test results in terms of the residual pollution layer resistance, arc development speed, arc extinguishing conditions, and simulation parameters. The test results and model simulation results are mutually verified.

通过本方法预测得到的最低闪络电压与真实绝缘子闪络电压契合度较高，对于实测XP-70绝缘子，预测值和真实值之间差异<5%。The minimum flashover voltage predicted by this method has a high degree of fit with the real insulator flashover voltage. For the measured XP-70 insulator, the difference between the predicted value and the real value is less than 5%.

以上所述仅是本发明的优选实施方式，应当指出，对于本技术领域的普通技术人员来说，在不脱离本发明技术原理的前提下，还可以做出若干改进和变形，这些改进和变形也应视为本发明的保护范围。The above is only a preferred embodiment of the present invention, and it should be pointed out that for those of ordinary skill in the art, without departing from the technical principle of the present invention, some improvements and modifications can also be made. It should also be regarded as the protection scope of the present invention.

Claims

1. predict a method for flashover voltage with surface conductivity and leakage current, comprise the following steps:

(1) insulator surface electrical conductivity is measured,

(2) using insulator surface electrical conductivity as input parameter, in conjunction with insulator form factor parameter, dynamic arc model is set up,

(3) leakage current development trend is calculated,

(4) obtain the minimum flashover voltage of insulator chain, judge insulation margin and the external insulation level of this insulator based on minimum flashover voltage;

It is characterized in that,

The step setting up dynamic arc model is as follows:

Setting insulator form factor, the initial value of given parameters;

Input the insulator surface conductivityσ recorded;

Suppose that voltage u (t) reaches crest in zero moment, arcing starts:

u(t)＝U _mcosωt (1)

Wherein, U _mfor voltage effective value, ω is angular frequency, and t is the time;

Plate suspension insulator residue pollution layer resistance is along with the change formula of arc root radius and arc length:

Wherein, L is leakage distance total length, L _arcfor the arc length under conditions present; σ _efor surperficial pollution layer conductivity; r ₀for arc root radius, tried to achieve by following formula:

Wherein, corresponding under this state leakage current I _arctried to achieve by formula (4):

Wherein, u (t) is now voltage, R _pfor insulator residue pollution layer resistance, r _arcfor the arc resistance of unit length, L _arcfor the arc length under conditions present;

By following formulae discovery electric arc field intensity E _arcwith residue pollution layer field intensity E _p:

E _arc＝63I _arc ^-0.5(5)

Electric arc extends condition:

E _arc＜E _p(7)

Work as E _p<E _arctime, along with the change of voltage, the expression formula of arc length variations is such as formula shown in (8):

Work as E _p>E _arctime, the expression formula of arc length variations is such as formula shown in (9):

Arc length variations also has additional extension parameter μ;

Set up the dynamical equation of unit length arc resistance change:

Wherein, N ₀for the dissipated power of unit long arc; τ is time constant, is calculated by following formula:

Wherein, Q ₀for test gained dissipated power constant;

The extinguishing condition of definition electric arc is:

R _arc>R _n(12)

Wherein R _arcfor electric arc all-in resistance, R _arc=r _arcl _arc; R _nbe the resistance value of a setting, if now because arc resistance is much larger than the resistance in dry district, electric current flows through residue pollution layer, arc extinction by dry Qu Houzai;

After arc extinction, under surface conductivity σ is at this moment described, U _mbe not enough to make insulator generation flashover, therefore increase U _m, until obtain a minimum U _m, make insulator generation flashover, this value is the minimum flashover voltage of this insulator chain obtained.

2. the method for surface conductivity according to claim 1 and leakage current prediction flashover voltage, is characterized in that,

Above-mentioned Parameters in Formula value is: N ₀=60, Q ₀=0.075, μ=5.